Method of and apparatus for telegraphic transmission



Dee. 19, 1922. I 1,499,633. J. W. IVIILNOR.

METHOD 0F AND APPARATUS FOR TELEGRAPHIC TRANSMISSION.

FILED SEPT. I 7. 19.18.

Patented Een. i9, i922.

, serra COMPANY, or nnwonir', n.

stares rarsnr orifice.

JOSEPH V7. MILNOR, @F.NETT YORK, N. Y., ASSIGNOR lT0 THE WESTERN UNIN `TELE-y Y., A coarorafirion or NEW Yoan.

METHOD OF AND APPARATUS FOR TELEGRAPHEC TRANSBTISSION.

Appiiceadn inea septemberi?, isis. serial No. 254,401.

TOMU ift/wm t Hwy concern Be it lrnoivn that l, Josnrii WV. MiLNor., a citizen of the United States of ifiinerica, and a resident of New York, inthe county ot 'New York and State of Nen7 York, have niented certain. nen.T and useful lmprovements in the Methods oi? and Apparatus' for 'ilelegraphic rlransmission, of Which the iollowing is av specification.

h/ly invention relates to a method ot and apparatus for telegraphic transmission, particularly duplex telegraphic transmission, through lines of high static capacity, such as iong submarine cables. By the 'tcriiiliiies of high static capacity l mean lines 'such as it is substantially impracticable to operateA by direct applicationy ot battery or-other source ot' current to the line and by f ordinary contact-making and contactbreaking` relays the receiving end; to thek contrary, lines oit high, static capacity, as that term is employed herein, means lines which innst belivorked through condensers, and iii which the current limitations are such that the receiving instrument finust be oit the nature ot a siplion recorder, or simiiar very delicate receivinginstrument, except as the nature lot' the receiving instrunient may be atiected by the so-called cable inagiiiliers which are now coming` into er;-` tensive use. y

My invention comprises improvements in methods and apparatus tor telegraphic transmission through such lines of high.` static capacity, whereby increased speed ot operation, iliarticularly in the case oiI duplex transmission, .is obtained, and whereby energy is available at the receivingl .r the operation oit' the recieving ap-l My invention is particularly apili able .vhen' a `cable magnifier is employed A iic receiving; end, but is independent ot ani* particular 'torni of magnifier; for eX- aiiiple, the in an'iiitier maybe ot the hot Wire type, such as the well known lfleurtley mag'- nitier; or it-,niay be a selenium relay or other instrument working upon the prinziple oi'inovenient ot' a beam ot ligl'it- 'across an electrically light-sensitive surface; or it may vhe a magniiier employing the so-called relay or audion, as set forth," `for exam ple, in my prior application ySerial No. 212,-

- 32, tiled Januar' li, 191:8,novv ,5578,71 2. granted May i7, 1921,

and No, lilS, granted May 9,1992, respectively.

liind' that the. .employment ot a magni tier very vgreatly .modifies conditions .of cable transmission, making desirable the'sup pression oi',i certain features which liereto- Fcor eX- bei'ore the employment oft magniit was .not necessary as a rule lto payr great attention `to the matter of obtaining as iieariy per'ect duplex balance as possible,

iinssion rpracticable Without magniiiera and flic conditions ot transmission obtaiin L y iout inagnitiers, it was usually possible to obtain, without rgreat difficulty, a' sut'iciently accurate balance. But the introduction ot magnitiers produces a quite d-itif'ereiit condition. 'iVbeii ,940ml meg-Hitlers are used,the message capacity .oit a cable is p actically limited only by the 'accuracy oi thednplex balance obtainable; and any device which makes it possible to obtain a better duplex balance, or tor any reason decreases the perfection ofiI balance required.

materially increases the message capacity oi' the cable.

Asis Well known, in the duplex operation ottelegraphl lines, there is employed, .in addition to -the main line itself, a so-called artiicial line at each transmittingpoint,

which artificial line is supposed to be a du-v plication, as -to `resistance and capacity, of lthe main line.

ln practice, however.y it is found practically impossible to malte ythe artiticial line complete representation, in any` electrical sense, of the main line. 'For example, the main line has lits static capacity Well distributed throughout' its length; yet this distribution may not'be even, because the cable rline may be built up of various sections, .of differing construction; and from time to time the construction ot the cable is affected4 by patching 5 i. e., the replacingr of detective sections by new sections. Furthermore, leaks develop in cable lines from time to time, and, until repaired, greatly aie.-

tec't the distribution otlcapacity in the cable.

ers, gre t attention was paid to the obtain-` i rpossible at the receiving- Siphon recorder.` Y

the reason that at the speeds of trans-y Furthermore, the resistance of the main line cable is changing constantly due to change of temperature, and for the obtaining of a perfect balance. constant corresponding readjustment of resistance of the artificial line wouldbe required. lt is, therefore, practically impossible to have an artificial line which at all times and under all circumstances absolutely duplicates, in an electrical sense, the main line.

l have found that conditions of operation, particularly when operating duplex, are much improved and a much higher speed of transmission is made possible by modifications in the method of transmissiomand in the transmitting apparatus, whereby the rise of'current and potential in the line. incident to the closing of the transmitter contacts, is made more gradual; in other words, what may be termed a cushioning effect is introduced betweenk the source of current supply and the line; suc-h cushioning being oby tained by the introduction of relatively large resistances between the source of current supply and the line; the employmentof such relatively large resistances being usually accon'ipanied by the employment of a source vand the shuntec of current supply of higher voltage than that commonly employed heretofore. lt has not been unusual in ocean cable operation in the past to employ for current regulation relatively small resistances between the source of current supply and the line; such regulating resistances being usually of a few ohms only; but the cushioning resistances which l employ are of much greater valuefor eX- ample, to lO ohms each; such higher resistances being usually employed, as above stated, in connection with higher current voltage. ln one instance the voltage was increased about per cent. p To further aid in the production of the cushioning effect, I also commonly employ a condenser shunted around the transmitter contacts.

The effect of the high resistance employed condenser employed, 'as above referred to, is to smooth ont the rush of current into the cable, which follows the closing` of the transmitter contacts. By so smoothing out this rush of current, l find that the effect obtained with an actual imperfect balance between the cable and the artificial line, is practically the same as if hat balance were nearly perfect; and thereby a much higher speed of operation is obtainable than would otherwise be practicable.

ln addition I have found thatimprovement in conditions of transmission and reception may be obtained by changing the character of the signals sent byl the cable transmitter'u so as to increase the power available at the receiving end. i

As is well known, in cable transmission in the ordinary manner, current impulses of one direction denote dots of the telegraph code. and current impulses of the opposite direction denote dashes of that code. Normally. it may be said. there is no current to line; when a dotis to be sent, current of one po larity is put to line, and when a dash is te be sent, current of the opposite polarity is put to line. Between successive current im,-

pulses so put to line, of whatever direction,

there is usually an interval of no current, termed the curbing interval. rEhe result is what `are known as Curbed signals. ln contradistinction to this old method oftransmission, l find it better to entirely eliminate the no current interval between current iinpulses where dots and dashes succeed each other without intervention of regular spaces of the telegraph code. The result is what may be termed block signals distinguished from the former curbed signals. When two or more dots, or two or kmore dashes, succeed each other without intervention, one ,long impulse taires the place of the forn'ier successive impulses.

ln cable working it is very essential to so shape a wave of current received through the cable that the various dots and dashes composing the let-ters may be distinguished one Afrom the other. lf magniliers be not employed, the shape of these signals is iniproved by proper adjustment of the curbing interval commonly employed heretofore, as above mentioned, between impulses;y and. is also affected by the adj ustnxent of` magnetic shunts, receiving condensers, etc., at the receiving end of the cable. `But where cable magniliers are used, l find it desirable that the ,so-called refining or shaping of the cable signals be done at the receiving end; and to this purpose I do awayvvitli curbing intervals between the impulses, and by so doing make it possible to increase the energy transmitted through the cable; for in refining the signals at the transniitting end, by the employment of curbing intervals. and also in refining. at the receiving end, by means of magnetic shunts and receiving condensers, a large part of the energy of the signals is lost. Loss of energy at the transmit'ting` end is particularly undesirable when the balance between the cable and the artificial line is imperfect. Loss of energy at the receiving end, incident to the refining of the received signals, is not so important, however, part-ic ularly when a suitable magnifier is inv use especially since there is at the sametime a loss of energy of extraneous current (due to errors in balance) even greater than the loss of energy of the useful signals themselves. There is, therefore. a distinct gain to be made, when magniers vare employed, by the elimination of the curbing` intervals`r and by the reduction of the detrimental effects of imperfect balance; these being comparative resistance 2 messes improvements in soy tar as reduction ot Wasted energy and increase ot speed otope'rll ation are concerned; the relations of these two liinproyements being` so intimate, and their 'eilects cumulatively so important, that it is impossible to distinguish in a practicablesense bet'xveen improved results which can be laid definitely to the one improvement and improved results which can be laid detinitely to the other improvement.

.i vill noir vproceed toy describe my inyention with reference to the accompanying mechanism of thel Well known @Wheat-stone transmitter tor the operation of the controlling .contacts ofthe circuits ot Figure 2. Figure 4 `is `a Vdiagram illustrating transmission according to my improved method, Without curbing intervals between impulses; and Figure 5 isa similar diagram illustrating, `by' contradistinction, the former method of transmission employed and en'ibodying the use ol:` curbing intervals.

Referring iirst to Figure l: l designates a transmission battery., 2, 2 the cushioning reinstances referred to, 3 the cushioning shunted condenser referred to, and el, 4l the transmitter keys, which may be thevarmature levers ot the relays shown in Figure 2. The battery l is connected, through the contacts otithe transmitter keys, yto thel apex ot the usual lillheatstone bridge arrangement of line and artificial line,`the usual blockcondensers '(3 being provided in two arms or" this bridge, with a condenser 7 and inductive resistance 8y connected across the bridge, to` gether with the additional shunted condenser Sand resistance l() in series With the magniiier ll 'in the cross Wire of the bridge. l2 designates the artificial line and i3 the main line or cable forming 4the other tu'o arms oi the lbridge. It Willbe obvious that the and condenser 3 materially cushion Vthe-rise ot potential inthe linel?) and artificial line l2 upon the closing ol:

the transmitter contacts l; which cushioninghas, I have explainedy above, the eilect of materiallyimproyingv the conditions as to balance between the main and artificial lines; producing the effect of a much more per-feet balance than actually exists.

llV'hile it would transmission `keys 4- by means other than -B is moved to the lettk tit no* be possible to operatetlie described, or even y hand, yet the means these shown in ik l is convenient and desirable. ln Fig-` the keys l constitute the armature levers 'relays A and E, each relay having three i ings, sho-Wn in Figure 2 as separate spools i, and iti, though it'will be understood by those skilled in 'tl e art that instead ot separat'l spools thesek windings it all be on the same spool. k17' desiges a source ot current supply for the Liperation of the relays, and i8, i9, and 2O are contacts, closed by the operation ot the mechanism shown in Figure 3, for the transni' ion oi' flots or clash g i9 beinga contact ci. seo y oi? dashes. 2t) a con dosed 'for tl: transmission of dots,

and a. grounding contact closed for the transmission oit either dots or dashes. lin .Figure 3 desi rites the perforated message tape ot the liheatstone transmitter, 22 and 23 designate the eelers of that transmitter, and 2a designates a member, operated by theusual camfmechanism of the ilitheatstone transmitter, whereby the teelers and 23 are al' ernately permitted to press againstthe paper strip v2l and then withdrawn tl'ieretrom. it will be apparent that as the eelers 22 and 23 are permitted to press against the paper strip, one or the other of suoli leelers will be permitted to pass tliroughthe strip it a perforation ot t 'ie strip be opposite that teeler, and thereby a dot or a dash contact will be closedc grounding contact l@ is opened and closed periodically at rr Alarly recurring intervals Whether or not the dot contact, or the dash contact, be closed. the operating speed of the cable be i cycles second, the contact i8 will close ien times in each second.

Normally, the arm-ture levers L:it ot' relays El and B are held locked against the particm lar contacts with which such armatures happen be in conta t at the moment, by a small current troni buttery l through Windwhich are in a high resistance circuit. Closing; oi the dash contact 19 closes circuit vfrom battery l? through contact 18 and contact i9 and Winch-ix lo of relay A, to return; ery l? through Contact i8 and i.

` 1 1g also-` trom 'indinp relays fr and il to ret and as a result t z nat-ure ot t already at the leltl while the armature 'of relay il is moved to the, right (it not already at the right); tor the circuit oi Winding i6 being of lower resistance than ot Windingl, exercises a piL-eponderating iniiuence on the armati-ire of relouy A. By' the closing of contacts resultthis movement 'ot the armatures, ting battery l is placed to line iny a direction iter sending a dash impulse. it, on the other hand, dot contact be closed, then circuit` is completed trom Abat- The' lci a dot impul being completed as bei'ore l5 ot the two relays', and i s ult ie armature et relay B is moved to the right (it not already there) while the armature oi' relay .fr is moved to the left (it not already there). is a result oi" the contacts thus formed by the armatures ot the relays, the cable battery l is placed to line in a direction suitable 'or the transmission above stated, contact iS is broken and closed periodically, whether or not either oi contacts l2) and 2O are closed, and as a result the circuit through windings iii oi the is is broken and closed periodically; :fh `periods oi' breiten circuit, circuit through windings per- 1, holding the armat es of the relays in 'die positions occupied. Une thin to be provided for in the obtaining of block signals from a mechanical transmitter is, the obtaining ot' the aero periods or spacesf as tor eframple, the spaces between letters,

words and sentences, without losing the block.

character of tie signals. This condition is provided for by the contact i8. li', now, in transmission, such a space occurs, contact i8 is closed by the action ofthe transmitter, while contacts i9 and 2O are preventedirom closing, and circuit is completed trom battery l' through winding l5. is a. result the armature ot relay it is moved to the left (if not already there) and 'the armature of relay ll is also moved to the lett (it not alruidy there). .iis result the connection oi the liuc to the cable battery through the line comflenscr is replaced by a connection to ground through the line condenser; and thus the spacingl signal is transmitted.

it will be seen that by the transmitting arrangement o'l l `igure 2 the transmitting keys i are always thrown instantaneously from one side to the other and in such manner that, practically speaking, the transmis" sion battery l is always to line in one sense or the other, curbing intervals being thereby eliminated.

ln some cases l find it desirable to employ an inductive resistance between the transmitting arrangement and the line and artilicial line, as indicated in Figure l; this in addition to the ohmic resistances 2 and shunted condenser 3.

it will be noted that according to my invention -ailjustments ol apparatus, etc. lor the purpose of shaping the signals, are to be made altogether at the receiving end; the condensers 7 and 9, inductance 8 and resistance 10, together with various features commonly provided in connection with the magnifier, or with the receiving instrument operated by the magnifier, or provided between the receiving instrument and the magnier, aitlfordingr ample opportunity for the shaping of the signals.y According to my invention, every effort is made to give the maxin'ium power to the impulses trans mitted, (while at the same time cushioning the transmission of these impulses into the line and artificial line, as above stated, to avoid troubles due to imperfect duplex balance), so that the impulses as received at the receiving end may be of as great power as possible.

l have shown diagrammatically in Figure Ll the uncurbed or block signals pre r'erred to be used in cable transmission, as above described, and, inr lFigure, I have shown, by contrast, the same signals as transmitted by the ordinary or curbing7 method. in these figures l have shown characters a, o, and w, as transmitted by uncurbed signals and bycurbed signals respectively. By comparison between Figure d, showing the preferred `method oi transmission, and Figure showing the hitherto common method of transmission by Curbed signals, the distinction between the block signals and the curbed signals will be apparent.

v`What I claim is:

l. The method of improving the balance between the main and the artiiicial lines in the transmission of telegraphic signals through submarine cables and lines of high static capacity, which consists in transmitting the signals in block form, the impulses being unseparated trom one another by curbing spaces, and cushioning the sudden rise oli current. f

42. The method of improving the balance between the main andthe artificial lines in the transmission oi' telegraphic signals through submarine cables and lines of high static capacity, which consists in transmitting the signals in block form, the impulses being unseparated irom one another by curbing spaces and interposing a non-reactive opposition ,to 'the sudden rise of current.

3. rlhc method ot' improving the balance between the main and the artificial lines in the transmission of telegraphic signals through submarine cables and lines of high static capacity, which consists in transmitting the signals in block form, the impulses being unseparated iti-om one another by curbing spaces, and restraining the sudden rise ot current without reactive etl'ect.

Li. ln a telegraph system., the combination with a submarine cable or transmission line of high static capacity, ofy means for nulliiiying the distorting effect of an imperfect balance between the cable and the artificial line, comprising means to transmit the signals in block iorm, and a .non-inductive cushioning resistance interposed between the source of current supply and the cable of sufficient value to prevent the sudden rise of current.

5. In a telegraph system, the combinaline of high static capacity, of means for nullifying the distorting` effect of an imperfect balance between kthe cable and the artificial line, comprising means to transmit the signals in block form, a non-inductive cushioning resistance interposed between the source of Current supply and the cable of su'lieient value to .prevent the sudden rise of current, and a eondensershunted around the transmitting means.

6. In a telegraph system the combina tion with a source of current supply and a line1 of means for supplying` current of one sign or the other at will from said source to said line comprising two transmitting keys, electro-magnetic operating means for said keys comprising for each a holding winding and two other windings opposed relatively to each other and arranged the one to exert a weaker influence than the other, and means controlling the iiow of current through said relatively oplpmsed windings and eomprising'two contacts arranged to he closed alternatively and at will and one controlling the stronger of the two opposed windings of the one key and the other the stronger of the two opposed windings of the other key, together with a third Contact closed when either of the irst two mentioned contacts is closed and Controlling the weaker of the opposed windings of said two keys. f

In testimony whereof l have signed this specification in the presence of two sul seribing witnesses.

JOSEPH W. MILNOR.

, Witnesses:

IALAN STANDISH DANA, RANDOLPH LEDORN, 

